Extraction
萃取
GrindingDefinition
The process of dissolving soluble compounds from ground coffee into water, driven by contact time, temperature, turbulence, and the surface area of the grind. In a well-brewed filter coffee roughly 18 to 22 percent of the dry coffee mass ends up in the cup; the rest is mostly cellulose and fiber. Flavor depends not only on how much dissolves but on which compounds come out first - fruit acids and sugars lead, bitter and drying molecules follow.
Etymology
From Latin ex-, 'out', plus trahere, 'to draw' - literally to draw out. Chemists used it for solvent-based separation long before coffee writers borrowed the term.
In use
The frame every brewing guide uses to diagnose a cup: 'the extraction is uneven' can cover both weak spots and bitterness in one word.